The present invention relates, in general, to integrated circuits and, more particularly, to integrated mixer circuits for providing frequency translation.
In electronic systems such as cellular or wireless telephones, a frequency relationship exists between an incoming signal and a signal generated by a Local Oscillator (LO). The incoming signal can be a modulated signal containing information that is recovered in a receiver of the electronic system. The modulated signal and the signal generated by the LO can be mixed to translate the carrier frequency of the modulated signal from the Radio Frequency (RF) range to a signal having a frequency in an Intermediate Frequency (IF) range.
Typically, the signal generated by the LO has a large amplitude compared to the amplitude of the received incoming signal. A high amplitude incoming signal can affect the frequency of the LO signal and "pull" the frequency of the LO signal away from a desired nominal frequency and toward the frequency of the incoming signal. Generally, the frequency of the signal generated by the LO is substantially independent of the frequency of the incoming signal. Alternatively, the amplitude of the incoming signal can affect the impedance of a tank circuit that defines the frequency of the LO signal. The change in impedance of the tank circuit "pushes" the frequency of the LO signal away from the frequency of the incoming signal. To prevent either "pulling" or "pushing" of the LO signal frequency away from the desired nominal frequency, the amplitude of the received incoming signal should be low and the frequencies of the incoming signal and the LO signal should be far apart.
Accordingly, it would be advantageous to have a method and a receiver circuit for translating the frequency of the incoming signal. It would be of further advantage to have the receiver circuit operate with an LO signal that has a frequency substantially different from the frequency of the incoming signal.